Testing the 135gr Apex-Outdoors Afterburners

[Petey308]

I had to go back to some of my old notes, but as a point of reference for an 18" barreled 308 Win, we had an ammo company work up a compressed load of TAC at 44gr with the 153gr prototype and took it to 2800 fps. It was the fastest that gun had ever pushed a 150 class bullet out. There was a node at 2750 fps and 43gr that he really liked though, and that's where he settled.

So, that's our heavier 153gr with only an 18" barrel. Hence my belief in the 135gr out of your 24" barrel really hauling the mail.

Yeah, I've pushed a 195gr TMK to 2700fps from that particular rifle . I'm pushing a 155gr TMK from my 18" AR-10 at 2700fps but that's a very intentional MV.

So I'm confident this slick bore rider bullets should move pretty quick lol.

Right around 43gr is a very common node with most 308s, loads, and applicable burn rate of powder. One of these batches I loaded happens to be right at 43.0gr.

 

[bamban]

Speed king for 308 is 2000 MR. Launching 168 Hybrids through my purpose built 1000 yard M1a at 2800. Not for the faint of heart. Hiwever, three of my former teammates still run the load at 1K matches.

@Petey308 did you measure the bearing surface difference netween the 137 and 135?

 

[Petey308]

Speed king for 308 is 2000 MR. Launching 168 Hybrids through my purpose built 1000 yard M1a at 2800. Not for the faint of heart. Hiwever, three of my former teammates still run the load at 1K matches.

@Petey308 did you measure the bearing surface difference netween the 137 and 135?

Which 137gr? And measuring bearing surface can be tricky with monos when they have drive bands, bore riders, etc and then differences still on things like the angles going into and out of the bore rider, radiused edges, etc, etc.

It tends not to be as easy as comparing bearing surface on lead core bullets. Even then, differences in jacket thicknesses can vary the amount of friction and engraving forces, and thus pressure, even with bullets that otherwise have the same bearing surface length. I suppose differences in copper alloys and their hardness can vary those things too with monos.

So measuring the bearing surface length and comparing them on certain monos might not be as meaningful as you light hope. Any data is worth knowing and comparing though, for whatever it may be worth. If I had some of those 137gr HH I'd definitely measure what I could and do a comparison.

 

[Petey308]

Speed king for 308 is 2000 MR. Launching 168 Hybrids through my purpose built 1000 yard M1a at 2800. Not for the faint of heart. Hiwever, three of my former teammates still run the load at 1K matches.

@Petey308 did you measure the bearing surface difference netween the 137 and 135?

I'm not a real speed demon and where I live and hunt, temp stability is more of a concern. So powders like 2000 MR, 748, CFE 223, etc are great at producing top speeds in a 308, but having to use multiple charges weights for hunting year round (coyotes are no limit and all year in Missouri) I've steered away from ball powders and temp sensitive extruded powders unless it's not for hunting or precision shooting.

Personal preference is all.

 

[bamban]

Which 137gr? And measuring bearing surface can be tricky with monos when they have drive bands, bite riders, etc and then differences still on things like the angles going into and out of the bore rider, radiused edges, etc, etc.

It tends not to be as easy as comparing bearing surface on lead core bullets. Even then, differences in jacket thicknesses can vary friction and engraving forces, and thus pressure, even with bullets that otherwise have the same bearing surface length. I suppose differences in copper alloys and their hardness can vary those things too with monos.

137 HH

 

[Petey308]

137 HH

No. I don't have any to measure either.

 

[Petey308]

Got the initial rounds shot today. The following below is the data gathered from those rounds:

135gr Afterburner

42.0gr

1- 2953
2- 2953
3- 2962
A- 2956
SD- 5
ES- 9

42.5gr

1- 3004
2- 3011
3- 2993
A- 3002
SD-9
ES- 18

43.0gr

1- 3003
2- 2996
3- 3017
A- 3005
SD- 10
ES- 21

So that's exciting and means it is faster like we thought and capable of the 3000 ft./s mark. So with all that data plugged in to QuickLoad and with it now calibrated the estimated OBT node is 42.7gr with an estimated MV of 2991fps.

So next, I will load up some more rounds below, at, and above that estimated charge weight and then go shoot those and confirm where the actual node is.

 

[Mike D Texas]

Got the initial rounds shot today. The following below is the data gathered from those rounds:

135gr Afterburner

42.0gr

1- 2953
2- 2953
3- 2962
A- 2956
SD- 5
ES- 9

42.5gr

1- 3004
2- 3011
3- 2993
A- 3002
SD-9
ES- 18

43.0gr

1- 3003
2- 2996
3- 3017
A- 3005
SD- 10
ES- 21

So that's exciting and means it is faster like we thought and capable of the 3000 ft./s mark. So with all that data plugged in to QuickLoad and with it now calibrated the estimated OBT node is 42.7gr with an estimated MV of 2991fps.

So next, I will load up some more rounds below, at, and above that estimated charge weight and then go shoot those and confirm where the actual node is.

How do you calculate OBT from chronograph data and QL data?

 

[Petey308]

How do you calculate OBT from chronograph data and QL data?

By using MV and barrel time, along with a separate OBT calculator.

So I start with inputting as many of the data points as I can to what I know and can measure, like COAL, case length, barrel length, water capacity, etc and get a safe starting load, then I shoot a few charges starting low and record the actual MV. I then tweak the burn rate (Ba) in QL until the MV is calculates matches my actual MVs as close as possible.

From there, I look at the time it says the bullet is in the barrel and adjust, compare that to the OBT on my calculator, and then adjust the powder charge up or down in QL until the time is as close to the OBT as possible.

 

[bamban]

By using MV and barrel time, along with a separate OBT calculator.

So I start with inputting as many of the data points as I can to what I know and can measure, like COAL, case length, barrel length, water capacity, etc and get a safe starting load, then I shoot a few charges starting low and record the actual MV. I then tweak the burn rate (Ba) in QL until the MV is calculates matches my actual MVs as close as possible.

From there, I look at the time it says the bullet is in the barrel and adjust, compare that to the OBT on my calculator, and then adjust the powder charge up or down in QL until the time is as close to the OBT as possible.

How does your OBT calculation compare with the published OBT chart with different nodes and barrel length?

 

[Petey308]

How does your OBT calculation compare with the published OBT chart with different nodes and barrel length?

I'm not entirely sure what you mean, but my OBT calculator is an excel spreadsheet and I just plug in the barrel length and starting node I want and it spits out the corresponding numbers

 

[bamban]

I'm not entirely sure what you mean, but my OBT calculator is an excel spreadsheet and I just plug in the barrel length and starting node I want and it spits out the corresponding numbers

This.

 

[Petey308]

I use this

http://www.the-long-family.com/Xpert_Bullets_OBT_Tool_V2.xls

 

[bamban]

I use this

http://www.the-long-family.com/Xpert_Bullets_OBT_Tool_V2.xls

I am quite familiar with the link, I am just curious how your calculations compare with the published chart.